Title text: Note that this implies you should NOT honk solely because I stopped for a pedestrian and you're behind me.

Explanation

This explanation may be incomplete or incorrect:Please rewrite the last sentence so that it is less incorrect. What the hell, the second last one too.If you can address this issue, please edit the page! Thanks.

This comic is a riff on bumper stickers that say "honk if you love ____". Here, the subject is formal logic, but the word "if" is replaced with a formal logic term "iff," which means "if and only if".

"If and only if" connects two statements, saying that either both statements are true, or both are false. In this case, either someone likes formal logic and honks, or doesn't like formal logic and doesn't honk. The title text further elaborates on this, describing a practical situation (that is, stopping for pedestrians) and dissecting it with formal logic terms.

The joke is the contained self-reference. You have to love formal logic to take the sticker serious and honk for exclusively that reason.

But if you don’t love formal logic you would dislike the sticker at all and try to do something contradictory. And now the problem begins: If you don’t honk to contradict the sticker completely you automatically follow its instruction. So, there is nothing you can do except starting to love formal logic.

Transcript

[Vehicle with a bumper sticker that reads "Honk iff you love formal logic."]

Discussion

- What can we learn from this? - I've learned that everyone who drives a car loves Formal Logic that if they press a horn actuator while driving, a horn will sound (Thank you Mr. XKCD). Now can I comment if I love your undeniable genius and your unexpected life's lessons? - E-inspired (talk) 14:36, 28 February 2013 (UTC)

"So, there is nothing you can do except starting to love formal logic"
That isn't what this comic means. It means "I am a fan of formal logic, and if you are too, you may honk to indicate this. If you honk for any other reason at all, don't be surprised if I jam a pitchfork up your ass."
Re-write, please. 108.162.219.58 08:37, 10 February 2014 (UTC)

Why would you even think that is correct? -Pennpenn 108.162.249.205 03:19, 29 January 2015 (UTC)